The present invention relates to an improved fluid flow control apparatus and more specifically to improved fluid flow control apparatus for use in association with a single pump which supplies fluid to both a vehicle steering apparatus and to an auxiliary apparatus.
A known fluid flow control apparatus which is utilized to control the flow of fluid from a single pump to both a vehicle steering apparatus and an auxiliary apparatus is disclosed in U.S. Pat. No. 2,892,311. This known control apparatus includes a priority valve assembly which is effective to insure that sufficient fluid is supplied from the single pump to the steering apparatus during simultaneous operation of both the steering and auxiliary apparatus. The priority valve assembly has a single valve member which is movable in a valve chamber to block fluid flow between an inlet port and a single outlet port in response to a pressure signal which indicates that the demand for fluid by the steering apparatus is not being satisfied. The steering apparatus includes a closed center steering valve which is utilized in association with a steering motor which is continuously connected with reservoir or drain. Therefore, when the steering apparatus is inactive, the steering control motor is connected with drain and is ineffective to hold the steered wheels against movement.
Another fluid flow control apparatus is disclosed in U.S. Pat. No. 3,750,405 and includes a priority valve which is utilized to insure that sufficient fluid is supplied to a steering unit. Still another known fluid flow control system is disclosed in U.S. application Ser. No. 583,591 filed June 4, 1975 by Raymon L. Goff and entitled "Diverter Valve for Power Steering With Power Beyond".